Method of dressing and truing abrasive wheels



Oct. 17, 1939. w, 5, LQCKE METHOD OF DRESSING AND TRUING ABRASIVE WHEELS Filed June 6, 1938 2 Sheets-Sheet 1 M Y/fbz T T ORNE VS.

2,176,350 METHOD OF DRESSING AND TRUING ABRASIVE WHEELS W. B. LOCKE Filed June 6, 1938 2 Sheets-Sheet 2 INVENTOR lI/z'Z/zam B Z0011:

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Patented Oct. 17, 1939 UNITED STATES METHOD or nn'nssmo AND 'mUmG ABRASIVE wnnnns- William B. Locke, Detroit, Mich assignor to Ex- Cell-O Corporation, Detroit' -Mich .a corporation of Michigan Application Julie 6, 1938, Serial No. 212,019

9 Claims. (Cl. 125-11) The invention relates generally to the dressing or grinding wheels and it has particular relation to the dressing of thread grinding wheels and resharpening of the diamond employed in the dressing operation.

Thread grinding generally is well known in the art and-is accomplished by using an abrasive grinding wheel having its outer peripheral edge shaped to fit between to form the threads and feeding the wheel along the work while rotating both the wheel and the work. The principal advantage of thread grinding is that the threads may be formed in a precision manner and with smooth surfaces and this is particularly important where accurate fits are required and where movements are to be acr irately governed by threaded members. It becomes apparent, accordingly, that if the threads on the work are to be ground in a truly precision manner, the form of the outer peripheral edge portion of the grinding wheel must be accurately maintained. The practice heretofore employed has been to dress this edge portion of the wheel at intervals so as u to in amanner compensate for uneven wear on the wheel and provide a fresh abrasive surface. This dressing of the grinding surfaces of the wheel is'effected by means of a diamond tool which is fed along the grinding surfaces so as to 30 remove a small amount of the abrasive and it is evident that the degree of precision depends upon the precision obtained in the dressing operation. In order to obtain a still higher degree of precision in thread grinding, the present inven- 35. tion takes into consideration the small amount of wear occurring on the diamond and contemplates resharpening of the diamond frequently to the end that in each dressing operation, a sharper diamond will be used. 7 40 One object of the present invention is to provide a method of dressing a grinding wheel by using a diamond tool, wherein the diamond is resharpened so as to compensate for wear on the diamond occurring during the dressing opera- 45 tion.

Another object of the invention is to provide a method of dressing a grinding wheel and resharpening the diamond, wherein resharpening I of the latter is effected by causing the diamond 50 to travel along and in contact with a surface on the grinding wheel that is designed and arranged to accomplish the resharpening.

Another object of the invention is to provide a method such as last mentioned wherein resharp- 56 ening of the diamond is effected during a continuation of the feeding movement of the diamond during the dressing operation.

Another object of the invention is to'provide a grinding wheel having surfaces so arranged with respect to the work grinding surfaces that 5 the diamond is resharpened during a continued feeding movement of the latter. Other objects of the invention will become apparent from the following specification, from the drawings relating thereto and from the claims 10 hereinafter set forth.

For a'better understanding of the invention, reference may be had to the drawings, wherein:

Figure 1 is a fragmentary, cross-sectional view of a grinding wheel on an enlarged scale, indil5 cating positions 2, 3, 4, 5, and 6 of a diamond tool during the dressing and resharpening operations.

Figures 2, 3, 4, 5, and 6 are detail views on a still larger scale, illustrating the positions respectively indicated at 2, 3, 4, 5, and 6 in Figure 1;

Fig. 7 is a view on the order of Fig. l, of a grinding wheel for grinding a different type of thread illustrating positions 8, 9, l0, and I l of the diamond during the dressing and resharpening operations;

Figs. 8, 9, l0, and 11 are detail views on a further enlarged scale illustrating the positions 8,

9, l0, and H, indicated in Fig. '7, respectively; and 80 Fig. ,12 is a generally diagrammatic view illustrating the manner in which a diamond is repeatedly worn and reshaped according to one form of the invention.

Referring to Fig. 1, the grinding wheel is in- 85 dicated at is and it is to be understood that the axis of the wheel is disposed to the right of the right hand edge of the drawing and parallel thereto. It is further to be understood that during the dressing and resharpening operation, the 40 wheel is rotated at a high rate of speed, which is the same as the speed of the wheel during the work gr nding operation. In the form of wheel illustrated, the outer peripheral edge portion of the wheel is provided with outwardly converging thread grinding surfaces l6 and I! joined by a, rounded surface l8 and having, respectively, at their radially inner edges partly rounded surfaces l9 and 20, respectively. Each of the roundedsurfaces l9 and 20 corresponds to one half of the rounded surface IB although inversely related thereto and it follows that when the edge portion of the grinding wheel is grinding a thread having a rounded bottom and top, the roundedsurface I8 of the grinding wheel will fit the bottom while the partly rounded surfaces l9 and 20 will grind one-half of the rounded tops of the two adjacent threads between which the edge portion of the grinding wheel is disposed. While different forms of threads may be ground and the grinding wheel correspondingly shaped, the form of wheel illustrated is for a Whitworth thread wherein the included angle between the surfaces l6 and I1 is 55".

While only one diamond tool is shown, as indithe other half of surface l8, the surface l1, and

Each diamond is mounted in a' the surface 20. suitable holder, as will be understood in the art. As shown by Figure 12, the diamond initially is fully conical and initially has a point 22 located at the apex of the cone and on its axis 23. It is to be assumed at this time that repeated practice of the invention to be explained presently has resulted in a fiat 24 on the diamond and a new cutting point 25.

As illustrated, the full boundary line on the wheel denotes the surface thereof following the dressing operation. The broken line 26 indicates the surface prior to the'dressing operation, while the broken lines 21 and 28 indicate the path of return travel of' the diamonds, respectively. Line 29 indicates the path of initial movement of diamond 2|, as well as the path of final return movement thereof, while line 30 indicates the path of initial and final return movement of the second diamond. Y

While the following description pertains only to the diamond 2!, it will be understood that the second diamond will be positioned reversely with respect to' diamond 2| and that it will co-' act with the lower side of the wheel '(as seen in the drawings) in the same manner as diamond 2| co-acts with the other side of the wheel.

Now referring to Figs. 2 and 3, it will be appreciated that the point in traveling from position 2 to 3 will be slightly worn, as indicated at 3|, and that in moving from position 3 to position 4, the wear will be increased, as indicated at 32 in Figure 4. While this wear is slight, and

' in fact with one out almost infinitesimal, it will be seen nevertheless that if the diamond were again used in the same manner, the dressing operation, when repeated, would produce a form not quite the same, because the point 25 would have been eliminated. Moreover,-the error in form, after repeated dressings, would become particularly noticeable on the radii' of the form. The primary purpose of the present invention is to eliminate this wear or flat 32 that is produced during the dressing operation and to maintain the diamond with a sharp point. For accomplishing the ."esults desired, the grinding wheel is provided with sides 33 radially inward of the surfaces 19 and 20 andthe diamonds, respectively, arecaused to feed along such sides 33 and in contact therewith. Each of the sides 33 is at a lesser angle to the radial plane of the wheel as compared to the angle of the surfaces l8 and I1 and the diamond thus will contact with the side in a different manner, as evidenced by Figure 5.

It will be seen in this figure that the fllat 24 now is substantially parallel to side 33 and that as the diamond travels along the side 33, the flat 24 is worn back sufficiently to eliminate the: wear or flat 32 and so to speak, produce a larger flat 34 that is parallel to the original fiat 24, and a. new sharp point 35 as shown by Fig. 6. It will now be appreciated that a new point. 35 has been produced in place of the point 25 and that this point is so disposed that when the diamond repeats the dressing operation, the new point willengage the surface of thewheel substantially in the same manner as the point 25 engaged the surface in the initial dressing operation.

While the parts are enlarged considerably and some variances may occur, it will be understood that the. general principle of the invention is to cause the diamond to travel along an additional surface of the grinding wheel after the dressing operation of the required threaded form is completed, which will compensate for the wear effected onthe diamond during the dressing operation and provide a new point on the diamond for the next dressing operation.

. After the diamond completes its travel over the side 330f the wheel, it is returned along the I path 21 that causes it to be separated from the grinding surfaces of the wheel that have been tained for the next dressing operation.

It was stated previously that repeated practice of the invention had produced 'the flat 24 and new cutting point 25 after beginning with a diamond having a cutting point 22 at its apex and on its axis. Figs. 1 to 6 and the description pertaining thereto show how during use of the diamond in the dressing of the wheel, the point 25 is eliminated by wear and the diamond reshaped, so to speak, to move the fiat 24 back and produce a new flat 34 and new cutting point 35. It should now be appreciated beginning with the diamond having the point 22 at its apex, as shown by Fig. 12, how the point will be eliminated during dressing of the wheel. as by wear say to the broken line 36, and how upon movement of the diamond along the side 33 of the wheel, the fiat 24 and new point 25 will be produced.

It will be understood that the axis of the diamond will normally remain at the same angle to the wheel axis and that adjustment of the diamond radially towards the wheel axis is required for each dressing operation so as to obtain the desired depth of cut. Moreover, since repeated reshaping of the diamond produces new cutting points that are located progressively farther from the axis 23 of the diamond, although each shifting of the cutting point is infinitesimally small, it will be necessary at times to adjust the diamonds laterally of the wheel axis, as indicated by arrows A and B in Fig, 1, so as to compensate for such shifting of the cutting points.

It is to be understood that the wear and the corrective action of the wheel on the diamond as illustrated are shown very greatly exaggerated and in actual practice it has been found that after about fifty repeated dressings, the actual shifting of the point of the diamond laterally with respect to the axis 23 of the diamond, as from 25 in Fig. 2, to 35 in Fig. 6, represents a movement of less than .0001 inch. The amount necessarily will vary with the type of abrasive wheel that is used. It must also be appreciated that the lateral shifting of the sharp point in repeated dressings will affect the width only of the thread form on the wheel, which is easily corrected by adjusting the position of the diamonds iii the direction shown by said arrows A and B, while the actual form of the radii, angle, and height of the thread form on the wheel is not affected in any way by repeated dressing of the wheel, hence an accurate form on the wheel face 42, and surfaces 43 and 44 that extend from the inner edges of the surfaces 40 and 4|, re-

- spectively. The grinding wheel in this case is adapted to produce a modified Acme thread, having a radius at the top and bottom corners of the thread. The one diamond adapted to dress I the upper half (as shown in the drawings) of the thread grinding surfaces travels along the path indicated by the line 46 and then along the surfaces '42, 4|, and 44 of the wheel, while the other diamond travels along path 45 and surfaces 42, 40, and 43. As considered prior to the dressing'operation, the surface of the wheel is.

indicated by the broken line 41 while the full line on the wheel indicates the surfaces after the dressing operation.

Referring now to Figs. 8 and 9, it will be apparent that as the diamond travels along the surface 42, the wear effected thereon is not undesirable, as it does not tend to destroy the point, but that as the diamond begins to travel down the surface 4|, as in Figs. 9 and 10, a rounded point 48 will be created, as shown by Fig. 10, and thus, if the e dressing operation were repeated with the diamond in the shape shown by this figure, the

dressed form would not be accurate as desired,

and particularly the radii at the top and bottom corners of the thread form would be incorrect. In compensating for this wear 48, the surface 44,

which maybe disposed at a slight angle to the 'axis of the wheel, is provided and as the diamond moves along this surface, it is worn back to sub- 'stantialy the broken line indicated at 49 in Figure 10, thus establishing a new sharp point on the diamond as in Fig. 11. Fig, 11 shows the diamond after it has completed its movement over the surface 44 and after. the side has been worn back to such brokenline 49. After the diamond leaves the surface 44, it is returned along a path, indicated at 50, substantially to its initial position, and it will be understood that in repeating the dressing operation, the diamond will be fed in an amount required to redress the surfaces. The diamond for dressing the lower half (as shown in the drawings) of the wheel operates in substantially the same manner although the position of the diamond will, of course, be reversed.

It is to be understood in connection with both forms of the invention, that as one diamond is feeding inwardly to dress one side of the wheel,

the other is returning to its initial position.

Moreover, it will be understood that the two diamonds will be mounted in a machine designed to accomplish the feeding and withdrawal movements in the manner stated.

The inventionthus provides a means for dressing a thread grinding wheel or the like in a precision manner and maintaining the uniformity of precision in repeated dressing operations without requiring frequent replacement or costly reconditioning of the diamond. Thus, the undesirable effects, particularly errors in the form of the work produced by Y the grinding wheel caused by worn diamonds, are eliminated, and a much greater precision in grinding thread forms is, therefore, obtained. When it is borne in mind that infinitesimal dimensions are involved in pre- 1 cision grinding, the importance of maintaining a sharp point on the diamond becomes manifest if the precision is to be maintained during re-' .economical dressing of the wheel at the same high speed as the speed used in the thread grinding operation. Even though this high speed wears the diamond more rapidly, reshaping and repointing efiects such as saving in diamond cost, that high wheel speed may be used in the dressin operation. Using this same high speed in the dressing operation is distinctly advantageous in that the dressed form is not altered by a change in centrifugal forces such as would occur if the grinding wheel were slowed down for dressing.

Moreover, using the same speed simplifies operation of the grinding machine as the necessity of changing wheel speeds for dressing is avoided.

Moreover, by using two diamonds for opposite sides of the wheel, respectively, and in the manner described and shown, diamonds having greater cone angles may be used and this means that the diamonds are stronger and will be more durable under high dressing speeds.

Although more than one form of the invention has been illustrated and described in detail, it will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the appended claims.

What is claimed is:

1. The method of dressing a work grinding surface of an abrasive grinding wheel and resharpening a substantially conical pointed diamond tool employed in the dressing operation, which comprises rotating the grinding wheel, feeding the diamond along the grinding surface of the wheel with the pointed portion of the diamond in contact with said surface so as to effect the dressing operation. and then feeding the tool along another abrasive surface on the wheel which is so arranged and related to the diamond that the latter is reshaped to provide a new cutting point.

2. The method of dressing a work grinding surface of an abrasive grinding wheel and resharpening a substantially pointed diamond tool employed in the dressing operation, which comprises rotating the grinding wheel, feeding the diamond tool along said grinding surface of the wheel with the pointed portion of the diamond in contact with said surface so as to effect the dressing operation, and then feeding the tool along and in contact with another surface of the grinding wheel adjacent the first surface to reshape the diamond so as to compensate for the wear effected during dressing of the first surface to the end that the diamond will be substantially repointed for a succeeding dressing operation.

3. The method of dressing a work grinding sur-' the pointed portion of the diamond in contact with'said surface so as to effect the dressing operation, and then feeding the tool along and in contact with another surface of the grinding wheel adjacent the first surface and angularly related thereto to reshape the diamond so as to compensate for the wear efiected during dressing of the first surface to the end that the diamond will be substantially sharpened for a succeeding dressing operation.

4. The method of dressing a work grinding surface of an abrasive grinding wheel and resharpening a substantially pointed diamond tool employed in the dressing operation, which comprises rotating the grinding wheel, feeding the diamond tool along said grinding surface of the wheel with the pointed portion of the diamond in contact with said surface so as to effect the dressing operation, and then continuing the feeding of the tool along and in contact with another surface of the wheel normally not engageable with the work to be ground and which is adjacent the first surface and angularly related thereto to reshape the diamond compensatory to the wear effected during dressing of the first surface to the end that the-diamond will be substantially sharpened for a succeeding dressing operation of said grinding surface.

5. The method of dressing a thread grinding wheel and resharpening a diamond tool employed in the dressing operation wherein the wheel has its outer edge portion provided with outwardly converging grinding surfaces to fit the thread to be ground, which comprises rotating the ,wheel, feeding the diamond inwardly along and in contact with one of said grinding surfaces to effect the dressing operation and then continuing the feeding of the diamond along a substantial extent of' surface of the wheel normally not engageable with the threaded work to be ground and which is adjacent the dressed surface and angularly related thereto so as to reshape the diamond in a manner compensatory to the wear effected during dressing of said grinding surface.

6. The method of dressing a thread grinding wheel and resharpening a diamond tool employed in the dressing operation wherein the wheel has its outer edge portion provided with outwardly converging grinding surfaces to fit the thread to be ground, which comprises rotating the wheel, feeding the diamond inwardly along and in contact with one of said grinding surfaces to effect the dressing operation, then continuing the feeding of the diamond along a substantial extent of surface of the wheel normally not engageable with the threaded work to be ground and which is adjacent the dressed surface and angularly related thereto so as to reshape the diamond in a manner compensatory to the wear effected during dressing of said grinding surface to the end that the diamond will be substantially sharpened for a succeeding dressing operation of said grinding surface, and then withdrawing the diamond along its previous path but in spaced relation to the dressed surfaces of the wheel.

'7. The method of dressing 2:. 'work grinding surface of an abrasive grinding wheel and resharpening a diamond tool wherein the latter has sides converging to substantially a point, which comprises rotating the wheel, feeding the diamond along and with its point in contact with the surface soas to dress the latter with the tool so positioned that normally the point of the diamond will be worn to produce a fiat, and then continuing the feeding of the diamond along and in contact with a surface of the wheel, adjacent to and which is so angularly related to the dressed surface and of such extent that the flat will be changed by wearing so as to repoint the diamond substantially to its original sharpness.

8. The method of dressing a work grinding surface of an abrasive thread grinding wheel and resharpening a diamond tool wherein the latter has sides converging to substantially a point and wherein the wheel has its outer edge portion provided with converging surfaces shaped to fit a thread on the work to be ground, which comprises rotating the wheel, feeding the diamond along and with its point in engagement with one of the thread grinding surfaces so as to dress said surface during which the point on the diamond is substantially flattened by wearing, and then, feeding the diamond along and in contact with an additional surface of the wheel adjacent to and which is so angularly related to the axis of the diamond that generally the latter is reshaped to provide a new cutting point.

9. The method of dressing a work grinding surface of an abrasive thread grinding wheel and resharpening a diamond tool wherein the diamond has sides converging to substantially a point and wherein the wheel has its outer edge portion provided with outwardly converging thread grinding surfaces arranged at acute angles to the plane of the wheel and adapted to fit a thread to be ground, which comprises feeding the diamond inwardly along and with its point engaging one of said grinding surfaces so as to dress said surface, and then continuing the feeding movement of the diamond along and in contact with a surface of the wheel which is disposed inwardly of the grinding surface and arranged at a lesser angle to the plane of the wheel than the angle of the grinding surface, whereby wear on the point of the diamond during the dressing operation is compensated for by reshaping of the diamond during its engagement with the inwardly disposed surface;

WHJLIAM B. LOCKE. 

